Pretty cool. I like your Mars effect. Some shadows and volumetric fogging would do wonders for your demo though. Also, how long did you spend on this? I may be interested in implementing the same effect since I'm working on lot with terrain right now.

The Nut: shadows and clouds ( various types ) are on my TODO list. I will have to think about volumetric fog too.

If your engine is capable of using shaders then implementing scattering effects should be relatively fast. It took me one week to read the theory, understand it, write GLSL shaders and some C++ code. I was really surprised that it took me so little time